On the default Dokuwiki template, there should be a file called tpl_header.php, which generates the headers. You'll see a little snippet at the bottom to generate the breadcrumbs. See
here:
<!-- BREADCRUMBS -->
77 <?php if($conf['breadcrumbs'] || $conf['youarehere']): ?>
78 <div class="breadcrumbs">
79 <?php if($conf['youarehere']): ?>
80 <div class="youarehere"><?php tpl_youarehere() ?></div>
81 <?php endif ?>
82 <?php if($conf['breadcrumbs']): ?>
83 <div class="trace"><?php tpl_breadcrumbs() ?></div>
84 <?php endif ?>
85 </div>
86 <?php endif ?>